VOL. LIV.] PHILOSOPHICAL TRANSACTIONS. 'j^^ 



members of your celebrated society. When I made the reduction of these obser- 

 vations at Rodriguez, I found myself under disagreeable circumstances; and it 

 was probably my uneasiness at that time that occasioned a want of due attention, 

 which I was the longer in finding out as I could not easily suspect it. My clock 

 went too slow that day at noon by 1"" 2% so that I ought to have added J" 2' to 

 the time of the clock, whereas I subtracted as much from it. This is the reason 

 of the difference in the times. The small variation in the distances of the limbs 

 was owing to a stricter verification of the parts of my micrometer. 



XXIX. On the Transit of Venus. By Christian Mayer, S.J. Translated 

 from the Latin hy James Parsons, M.D. p. l6l. 



These observations were made at Schwezinga, belonging to the elector pala- 

 tine; but neither the latitude nor the longitude of the place were known. 



True time. 

 The interior contact of the western limb of Venus, with the 



western limb of the sun, observed with Dollond's telescope . . 20*^ 53°" 8' 

 The moment of the egress, when the same limb of the sun 

 after the interior contact first appeared corniculated, most ac- 

 curately observed with the same telescope, was 20 53 35 



Whence he concludes that the interior contact happened 20 53 33^. 



As to the instant of the exterior contact, he sent only two observations made 

 by him with certainty, because of the intervening clouds: the first shows the 

 time when he distinctly saw through the clouds the certain emersion of Venus, 

 -iV part of the diameter of Venus, as nearly as could be judged, excavating the 

 limb of the sun ; the other when, from the unlucky clouds, he could no more 

 observe the least vestige either of the emersion, or exterior contact, or of Venus. 



The first outer contact 21'^ Q"* 4* 



The other time of the certain emersion .. . .24 17 27 



XXX. Astronomical Observations. By Christian Mayer, S. J. Astronomer to 

 the Elector Palatine. From the Latin. Dated Heidelberg, April \7 , 1764. 

 p. 165. 



The following observations of a lunar eclipse were made March 17, 1764, at 

 Schwezinga, near Heidelberg, in the Palatinate, with a Dollond's 10-feet tube. 

 — The penumbra began at 1 1'' 3*" 24' true time; the penumbra denser at 1 1** 

 8"" 11'; the beginning of the eclipse, doubtful, ll'' 13"' 8'; the same was visibly 

 begun 11'' 14™ 9'; end of the eclipse, doubtful, 14*' 0"" 11'; the same certain 

 j4h |m. gjjj of jj^g penumbra 14*^ 4"*. The greatest obscuration was 8'' 39'. 

 And the moon's diameter measured 33' 49". 



Observation of the solar eclipse made at the same place, April 1, 1764. — The 



